Chair back



FIG. 1 is a perspective view of a chair back according to the present invention;

FIG. 2 is a back elevational view of the chair back of FIG. 1; and,

FIG. 3 is a cross sectional view taken along line 3—3 of FIG. 2.

The broken lines shown in FIG. 1 are for environmental purposes only and form no part of the claimed design. 

The ornamental design for a chair back, as shown and described. 